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| − | | + | #REDIRECT[[:Category:Yersinia species]] |
| − | ===Overview===
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| − | *Cause [[Intestines - disease due to pathogens|intestinal disease]] in animals and are important zoonoses
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| − | *10 species of which ''Y. pestis, Y. pseudotuberculosis and Y. enterocolitica'' are pathogenic to animals and humans; ''Y. pestis'' is the most pathogenic
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| − | *Rodents provide a reservoir of ''Y. pestis'', which is the cause of human plague; fleas transmit the infection to other animals and humans
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| − | *''Y. pseudotuberculosis and Y. enterocolitica'' reside in the intestine of domestic and wild animals and birds
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| − | *Birds may cause mechanical transfer of the organisms
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| − | ===Characteristics===
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| − | *Enterobacteria, but grow more slowly and at lower temperatures than other enterobacteria
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| − | *Gram negative, non-spore forming, facultative anaerobes - rods or colibacilli
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| − | *Non-lactose fermentors
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| − | *Facultative intracellular pathogens
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| − | *Show bipolar staining in Giemsa-stained smears from animal tissue
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| − | *Pathogenic strains identified by serotyping and biotyping
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| − | ===Pathogenesis===
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| − | *''Y. enterocolitica and Y. pseudotuberculosis'' enter the intestinal mucosa via M cells of the Peyer's patches
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| − | *Engulfed by macrphages in the mucosa
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| − | *All three invasive species are facultative intracellular organisms and grow inside macrophages
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| − | *Plasmid and chromosomal-encoded virulence factors required for survival and multiplication in macrophages
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| − | *Survive in phagolysosomes and do not interfere with degranulation or lysosomal fusion
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| − | *Resistant to macrophage killing mechanisms
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| − | *Antiphagocytic proteins secreted by the organisms interfere with host neutrophils
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| − | *''Y. pestis is more invasive than the other species and also possesses and antiphagocytic capsule and a plasminogen activator which aids systemic spread; endotoxin also contributes to its pathogenicity
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| − | *Transport within macrophages to mesenteric lymph nodes
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| − | *Replication in lymph nodes and development of necrotic lesions, with neutrophil invasion
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| − | *The bacteria destroy the macrophages causing septicaemia
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| − | ===Clnical infections===
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| − | *''Yersinia pestis''
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| − | **Cause of bubonic plague in humans, transmitted via fleas from infected rats
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| − | **Not a significant veterinary disease
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| − | **Disease in rats and other rodents similar to the disease in humans
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| − | **Bubonic form can lead to the pneumonic form, which is highly contagious and usually fatal
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| − | **Humans and domestic and wild animals incidental hosts
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| − | **Plague has rarely been reported in dogs, cats, camels, elephants, deer
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| − | **Cats can acquire the disease from ingesting dead rodents, and show lymphadenopathy and abscesses
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| − | **Fever, lethargy, swelling and abscessation of lymph nodes particularly in head and neck region
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| − | **50% mortality if not treated
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| − | **Possesses 3 plasmids, 2 of which are unique to this species; these encode an endotoxin, and coagulase and fibrinolytic activity
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| − | *''Yersinia pseudotuberculosis''
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| − | **Less virulent than ''Y. pestis'' but closely related
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| − | **Mainly infect in animals
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| − | **One plasmid, required for virulence
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| − | **Sporadic cases of pseudotuberculosis in animals and man
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| − | **Wild birds and rodents provide a reservoir of infection by harbouring the the pathogen in their intestinal tract
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| − | **Sources include food and water contaminated by faeces
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| − | **Multiplication in macrophages leads to granuloma formation
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| − | **Granulomas occur in the gut wall and mesenteric lymph nodes
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| − | ===Diagnosis===
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| − | ===Control===
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| − | ===Treatment===
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